Apparatus for high pressure impact coating

Abstract

A process and apparatus for high pressure impact coating of portions of workpieces such as the threaded openings in fasteners in avoidance of contaminating undesired portions of the workpieces with the coating material. A metered quantity of coating material is charged into a passageway and moved by low pressure air to a chamber ahead of an atomizing nozzle. High pressure air is introduced to the passageway and the coating material is fogged into a chamber defined by the workpiece and cooling. Proliferation and impingement of the cloud on the selected surfaces follows under vented conditions. A constriction in the vent line achieves the necessary delay and sets the system for accomplishing the coating. The machine structure facilitates use of the coating device with a wide range of female threaded fasteners and achieves the process steps while providing for flushing the lines and drying the working structure.

We claim: 
     
       1. In a machine for selectively locating and applying a coating to female threads on fasteners in avoidance of the coating material contaminating the balance of the threaded part, the combination comprising: a main passage defined through a tooling head;   a perforate nozzle connected at one end of said main passage;   a first tapered rigidly resilient ring seal surrounding said nozzle;   a second rigidly resilient ring seal in spaced-apart aligned relation with said first ring seal;   means for closing and opening said ring seals toward registering axial contact with each other and for impinging upon an intermediate fastener axially aligned between said ring seals, said fastener presenting a threaded female opening therethrough and into which said nozzle is thrust;   a metering valve for admitting a charge of coating material under relatively low pressure into said main passage upstream of said nozzle; and   a high pressure valve located upstream of said metering valve and selectively opening to blast said charge by high pressure air through said nozzle into the sealed cavity defined by said threaded part of said fastener and the closure of said seals on said fastener and said cavity thus formed having a communicating passage through which said high pressure air and surplus coating material are dissipated to ambient conditions at a selected rate.   
     
     
       2. A device for coating female threads in fastener elements and the like comprising: a pair of movable tapered ring seals in spaced-apart aligned axial registry, one of said seals surrounding a vent to ambient atmosphere and the other of said seals surrounding a diffusion nozzle and a nozzle connecting passage, said ring seals being adapted to seat against a fastener element having a threaded opening therethrough intermediate said ring seals and into which threaded opening said diffusion nozzle extends;   means for introducing a metered charge of coating material at said nozzle;   high pressure gas delivery means located upstream from said metered charge to drive said coating material through said nozzle and through said threaded opening defined by said seals; and   a constriction in said vent to ambient atmosphere providing means to controllably exhaust high pressure gas and coating material to the atmosphere.   
     
     
       3. In the device of claim 2 further including means for repetitively positioning fastener elements between said seals for coating. 
     
     
       4. In the device of claim 2 further means for periodically subjecting said nozzle and said seals to entry of a coating material solvent and air blast and means shifting said seals and said nozzle clear of closure against said fasteners for such periodic solvent treatment. 
     
     
       5. In the device of claim 2 further means for periodically subjecting said fastener elements in a line transverse to the axis of said seals and nozzle in consecutive alignment of said threaded openings with said seals and nozzle.